Guidewire with an intermediate variable stiffness section

ABSTRACT

The invention is directed to an guide wire for intraluminal deployment of a medical device within a patient, the guide wire having an elongate core member with an intermediate core section comprising a plurality of contiguous segments in alignment with the longitudinal axis of the core member with alternating flexible and rigid core segments, so that the articulated section bends in a discontinuous, discrete manner when advanced through a curved blood vessel or other body lumen within the patient. When an obstruction on a vessel wall causes the catheter or other coaxial device to be impeded, the guide wire and intermediate core section may alternately be advanced and retracted a short distance through the catheter distal tip causing a “nodding” motion of the catheter tip while the catheter is pushed through the vessel, so as to avoid and bypass the vessel obstruction.

BACKGROUND OF THE INVENTION

[0001] This invention relates to the field of intraluminal guide wiresfor advancing catheters such as stent delivery catheters, balloondilatation catheters, atherectomy catheters and the like, within bodylumens.

[0002] In a typical percutaneous coronary procedure, a guiding catheterhaving a preformed distal tip is percutaneously introduced into apatient's peripheral artery, e.g. femoral or brachial artery, by meansof a conventional Seldinger technique and advanced therein until thedistal tip of the guiding catheter is seated in the ostium of a desiredcoronary artery. For rapid exchange type catheters having a shortguidewire receiving lumen within their distal extremities, a guide wireis first advanced by itself through the guiding catheter until thedistal tip of the guide wire extends beyond the arterial location wherethe procedure is to be performed. Then a rapid exchange type catheter,such as described in U.S. Pat. No. 5,061,395 (Yock), is mounted onto theproximal portion of the guide wire which extends out of the proximal endof the guiding catheter which extends outside of the patient. Over thewire type catheters (OTW) have guidewire lumens which extend through theentire length of the catheter and with these types of catheters theguidewire and OTW catheters are advanced together within the guidingcatheter until the distal ends thereof are at the distal end of theguiding catheter. The guidewire is then advanced out the distal I end ofthe guiding catheter into the body lumen until the distal end of theguidewire is disposed beyond the procedure site.

[0003] In either case, once the guidewire is in place with the distalend distal to the procedure site, the intravascular catheter is thenadvanced over the guide wire, while the position of the guide wire isfixed, until the operative means on the catheter is disposed within thearterial location where the procedure is to be performed. After theprocedure, the intravascular catheter may be withdrawn from the patientor the guide wire repositioned within the coronary anatomy for anadditional procedure.

[0004] Further details of guide wires, and devices associated therewithfor various interventional procedures can be found in U.S. Pat. No.4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.);U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No. 5,341,818 (Abrams etal.); and U.S. Pat. No. 5,345,945 (Hodgson, et al.) which are herebyincorporated herein in their entirety by reference thereto.

[0005] Conventional guide wires for angioplasty, stent delivery,atherectomy and other intravascular procedures usually have an elongatecore member with relatively stiff proximal section and a flexible distalsection with one or more distally tapered segments. A flexible bodymember, such as a helical coil or a tubular body of polymeric material,is typically disposed about the distal section of the core member. Ashapeable member, which may be the distal extremity of the core memberor a separate shapeable ribbon which is secured to the distal extremityof the core member extends through the flexible body and is secured tothe distal end of the flexible body by soldering, brazing or welding, oran adhesive in the case of polymeric flexible bodies which forms arounded distal tip. The distal section is flexible and will not damageor perforate the vessel or body lumen through which it is advanced andthe portion behind the distal tip is increasingly stiff which bettersupports a balloon catheter or similar device.

[0006] The advancement of an intraluminal catheter over a guide wire maybe difficult where intravascular tortuosity, calcification,noncompliance, fibrotic plaque, previously deployed stents or otherobstructions are present proximal to the target site or lesion. With theuse of conventional guide wires having a core member of longitudinallyconstant stiffness in their proximal sections, the contact of theguidewire with vessel walls, e.g., adjacent a bend in the vessel, maycause the advancing catheter or other device to impinge or “catch” uponsuch an obstruction, impeding advancement.

[0007] The use of a guide wire of lower stiffness may lessen thefriction force of the catheter upon the vessel wall and obstruction, butthe reduced stiffness may lead to insufficient “pushability” andprolapse of the guide wire.

[0008] One useful approach to easing advancement of the catheter throughproximal obstructions is the use of a guidewire commonly called a“wiggle wire” which has a core length that is formed into a plurality of“kinks” or undulations where the core length has an S-shape. See forexample U.S. Pat. No. 5,007,434 (Doyle et al.) assigned to the presentassignee which is incorporated by reference herein in its entirety. Whenan obstruction is encountered, the portion of the “wiggle wire”guidewire having the undulating or S-shaped core segment is alternatelyadvanced and retracted through the catheter distal tip, causing the tipto “nod” laterally from side-to-side while the catheter is pushedthrough the vessel, so as to avoid and bypass the obstruction on thevessel wall. However, the guidewire with the kinked or undulating shapegenerally results in reduced steerability and control for the guidewire,and may require a larger guidewire lumen in the catheter to accommodatethe undulated shape which increases the catheter profile.

SUMMARY OF INVENTION

[0009] The present invention is directed to an guide wire for thedeployment of an elongated medical device within a patient's body lumen.The guidewire includes an elongated core member with a proximal coresection, a distal core section more flexible than the proximal coresection and a flexible body such as a coil or polymeric tube disposedabout and secured to the distal core section. The core member includesan intermediate core section disposed between the proximal core sectionand the distal core section, which has a plurality of segments orsub-portions which alternate between relatively stiff and relativelyflexible contiguous segments or sub-portions along a length of theintermediate core section. A flexible segment between two adjacent stiffsegments allow the intermediate core section to articulate whenadvancing through a tortuous body lumen so that the intermediate sectionbends discontinuously into discrete portions.

[0010] The segments of the intermediate core section are disposed in alinear arrangement and alternate between being relatively rigid or stiffand being relatively non-rigid or flexible, along a significant lengthof the intermediate core section. Thus, each flexible segment is boundedon each end by a stiff segment to allow articulation between the twostiff segments. When the intermediate core section of the guide wire isadvanced into a curved portion or bend in the vessel, the intermediatesection as a whole bends to conform overall with the vessel curvature.The flexible intermediate segments are substantially less resistant tobending than the stiff intermediate segments; so as a result most of thebending occurs in the flexible core segments, with the relatively stiffintermediate segments remaining relatively straight or otherwiseundeformed and articulating about the flexible segments.

[0011] When a catheter is advanced through a body lumen over aconventional guidewire and the leading edge of the catheter engages anobstruction in the wall of the vessel, such as a strut from a previouslydeployed stent, a ledge of fibrotic plaque, or the like, furtheradvancement of the catheter is impeded. However, utilization of a guidewire having features of the invention will allow the distal tip of thecatheter to oscillate or nod. The oscillation or “nod” motion of thecatheter's distal tip causes the distal tip to periodically reduce oreliminate contact with the obstruction while the catheter is pushedthrough the vessel. To provide the oscillation of the catheter's distaltip, the intermediate core section lies adjacent and across theobstruction. Either the catheter or the guide wire, or both, may bemoved longitudinally to an advanced or a retracted position a sufficientdistance so that the distal tip of the catheter has alternating contactwith bent flexible intermediate segments and straight stiff intermediatesegments which causes the catheter tip to “nod” laterally fromside-to-side. The distal tip of the catheter should oscillate or nod adistance of about 0.1 to about 3 mm, preferably about 0.5 to about 1 mm,in order to avoid or bypass the vessel obstruction.

[0012] The intermediate core section of the guidewire should have atleast one flexible intermediate core segment with proximally anddistally adjacent stiff intermediate core sections so that there is atleast one point, preferably about 3 to about 5 points or regions ofarticulation in the bending of the guide wire between the proximal coresection and the distal core section. Usually, not more than about 10points or regions of articulation are needed. The intermediate coresection preferably has multiple adjacent pairs of flexible and stiffintermediate core segments to provide an intermediate core section ofsufficient length for convenient manipulation by the physician or otheroperator as the section is alternately advanced and retracted asdescribed above.

[0013] The alternating stiff and flexible characteristics can beprovided to the intermediate core segments by dimensional changes ormaterial property changes along the length of the intermediate coresection. Dimensional changes to produce a periodically variablestiffness characteristic along the length may be made by centerlessgrinding or otherwise shaping a selected length of the intermediate coresection, or adding bands or sheaths to regions of the core, so as tohave a periodically variable stiffness along the core. For a core memberof substantially circular cross section, the cross-section of theintermediate section may also be circular, with the radius of the crosssection being variable longitudinally along a substantial length of theintermediate core section. The rigidity to bending of both the flexiblecore segments and stiff segments may be determined by selecting a crosssection for each based on material mechanical properties.

[0014] The transition of cross-sectional variations along theintermediate core section between the stiff and flexible segments ispreferably smooth. For example, the radius of the cross section may varylongitudinally in an undulating pattern, e.g. approximately sinusoidal,so that the intermediate core section has a longitudinal surface contourthat is undulating. As the intermediate core section is bent to conformto the curvature of a vessel, the inside surface contour (the contourfacing the inside of the bend or curve) will have a curvature which isdetermined both by the variation in diameter of the core within theintermediate section and by the variable curvature of the axis of theintermediate section.

[0015] The alternating sections may be of a range of selected overalllengths, typically from about 0.5 to about 10 cm, preferably about 1 toabout 5 cm. The pitch or spacing between like segments, i.e. flexible orstiff segments, may range from about 0.1 to about 10 cm. preferablyabout 1 to about 2 cm. The lengths and transverse dimensions of theintermediate core segments need not be the same along the length of theintermediate core sections. These dimension may be adjusted to providethe desired variations in stiffness along the length of the intermediatesection.

[0016] The ratio of the rigidity of the stiff segments relative to theflexible segments is substantially greater than unity, e.g. 1.1 to about1.7, preferably about 1.3 to about 1.5, and is selected to provide asubstantial longitudinal variation in curvature of the intermediate coresection, when bent to conform to vessel curvature prevailing in vesselsin which it is to be used. For a guidewire in which the variation instiffness in the intermediate section is due to variations in thediameter of the segments having a circular cross section, and whereinthe alternating variation in stiffness from segment to segment is due tovariation in cross section diameter as described above, the ratio of themaximum diameter of the stiff intermediate segment to the minimumdiameter of the flexible intermediate segment is about 5% to about 75%,preferably about 10% to about 20%. A typical example would be the stiffsegment having a maximum diameter of about 0.01 inch (0.25 mm) with anadjacent flexible segment having a diameter of about 0.0075 inch (0.19mm).

[0017] Alternatively, the variation in stiffness of the intermediatesection may be provided by longitudinal variation in material properties(e.g., by variable heat treatment or by a variation of materials), or bya combination of variation in cross section and variation in materialproperties.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is an elevational view, partially in section, of a guidewire having features of the invention.

[0019]FIGS. 2A and 2B are transverse cross-sectional views of theintermediate core section of the guidewire shown in FIG. 1 taken alonglines 2A-2A and 2B-2B respectively.

[0020]FIG. 3 depicts a catheter being advanced over a guide wire havingthe intermediate core section shown in FIG. 1, through a bend of a bloodvessel and bypassing an obstruction adhered to the vessel wall.

[0021]FIG. 4 illustrates an alternative intermediate core section of aguidewire core member embodying features of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022]FIG. 1 shows an embodiment of guide wire 10 having features of theinvention. The guidewire 10 has an elongated core member 11, a proximalcore section 12, a distal core section 13, an intermediate core section14 which has a variable rigidity and a flexible body or coil 15 disposedabout and secured to the distal core section 13. The distal end 16 ofthe coil 15 is secured to the distal end 17 of the core 11 by weld orsolder to form the rounded plug 18. The coil 15 is also secured to thedistal core section 13 by weld or solder at an intermediate location 20and at its proximal end 21.

[0023] The intermediate core section 14 has a plurality ofrelatively-rigid or stiff intermediate core segments 22 and a pluralityof relatively flexible intermediate core segments 23. As shown in FIG.2A, the stiff intermediate core segments 22 have a diameter d1, whereas,as shown in FIG. 2B the flexible intermediate core segments 23 have adiameter d2 which is much smaller than the diameter d1. The intermediatecore segments 22 and 23 alternate along a length of the intermediatecore section 14 and are joined end-to-end along the longitudinal axis 24of the guide wire 10. The alternating stiff intermediate core segments22 and the flexible intermediate core segments 23 have selected lengths25 and 26 respectively which typically range from about 0.5 to about 10cm, preferably about 1 to about 5 cm. The exterior contours of theintermediate core segments 22 and 23 smoothly transition between d1 andd2 to provide an undulating shape to the exterior of the intermediatecore section 14. The intermediate core section 14 may be covered with ahelical coil or plastic layer (not shown) which would have an outerdiameter essentially the same as the outer diameter of the proximal coresection 12. The core 11 is provided with a tapered junction 27 betweenproximal section 12 and the intermediate section 14. The distal coresection 13 may have one or more tapered sections 28 and 29.

[0024]FIG. 3 depicts the intermediate core section 14 shown in FIG. 1extending across the distal end of a catheter 30 which has been bent toconform to a curved vessel 31 shown in phantom. The leading distal edge32 of the catheter 30 is shown in phantom as engaging an idealizedobstruction or impediment 33. As a result of variable rigidity of theintermediate section 1, the guide wire axis 4 is not bent in acontinuous uniform manner, but rather in discrete portions. Thus, thelongitudinal axis 24 is essentially straight through the stiff segments22 and bent in the flexible segments 23 to provide a discontinuouscurvature as shown.

[0025] In FIG. 3 the catheter 30 is shown being advanced distally overguidewire 10 in the direction of Arrow A through a bend of vessel 31.The intermediate core section 14 of guidewire 10 is shown extendingacross the distal end of catheter 30 and out into the body lumen 31. Asthe catheter 30 is advanced, it conforms by contact to the inner contourof the guide wire 10. Note that inner contour 34 of catheter 30 hasnon-uniform contact with the surface of the intermediate core section 14of guidewire 10, as the stiff intermediate core segments 22 tend tocontact the interior surface of catheter 30 while the flexibleintermediate core segments 23 tend to either not contact the innersurface of catheter 30 or contact it with less pressure. As a result,the leading distal edge 32 of catheter 30 intermittently curves andstraightens laterally in the direction of Arrow C as the catheter 30 isadvanced (“tip nodding”).

[0026] In the example shown, the position of the obstruction 33 ispresumed to be initially in contact with a stiff intermediate coresegments 22, causing the distal edge 32 of catheter 30 to contact andbecome impeded or “stuck” at tip/obstruction contact point as shown inphantom.

[0027] However, when the guidewire intermediate section 14 is cyclicallyadvanced and/or retracted as shown by Arrow B, the intermittent contactwith the catheter 30 causes the distal tip 32 thereof to intermittentlycurve and straighten laterally, i.e. oscillate in the direction of ArrowC. Thus the cyclical motion of the intermediate core section 14 as shownby Arrow B produces a “tip nodding” motion even while the catheter 30 isin a static longitudinal position, cycling between lowered tip position32 a and raised distal tip position 32 b, as shown by Arrow C. Thus,when the catheter 30 is pushed in the direction of Arrow Asimultaneously with the cyclical motion of intermediate section 14 asshown by Arrow B, the resultant “tip nodding” motion permits the distalend 32 of catheter 30 to bypass over the obstruction 33 and advancebeyond it to tip position 32 c shown in phantom.

[0028] The guide wire 10 has other than the intermediate core section14, a construction generally similar to conventional guide wires. Theoverall guide wire length may range from about 100 cm to about 330 cmand typically about 170 to 190 cm. The guide wire distal segmentincludes a helical coil 15, but this may be replaced with a polymerjacket, or the like, which surrounds and covers at least a portion ofthe distal core section 13. The distal core section 13 is shown asextending to the distal end of the guidewire, but a separate shapingribbon may be used which extends from the distal end of the core memberto the distal end of the guidewire in a conventional fashion. The guidewire may be of conventional materials, such as stainless steel, highstrength precipitation hardened cobalt-chromium orcobalt-chromium-molybdenum alloys such as MP35N, Elgiloy and the like ora superelastic NiTi alloy with an A_(f) at or less than bodytemperature. The proximal shaft section 12 may be formed of a materialdifferent than the distal segmented shaft. The proximal core section ofthe guide wire core may have a diameter from about 0.007 to 0.035 inch(0.18-0.89 mm), preferably about 0.01 to about 0.014 inch (0.25-0.36 mm)for coronary uses.

[0029]FIG. 4 depicts an alternative embodiment of an intermediate coresection 40 suitable for use with a guidewire as described above. In thisembodiment, the intermediate core section 40 comprises a plurality ofalternating stiff core segments 41 and flexible segments 42. As in theembodiment of FIG. 1, the core segments 41 and 42 are joined end-to-enddisposed along the guide wire axis 43. In the embodiment 40, thediameter d4 is uniform along a substantial length of the core section40. The reduced rigidity of the flexible core segments 42 relative tothe stiff segments 41 is due to differing mechanical properties of thematerial from which these segments are composed, i.e., the stiff coresegments 41 can be formed of a relatively rigid material, while theflexible core segments 42 may be formed of a relatively non-rigidmaterial. The material compositions 34 and 35 may comprise the sameoriginal material which has been altered discontinuously along thelength of the intermediate core section 40 in such a way a to producethe desired variable rigidity, such as by intermittently heat-treating,cross-linking irradiation, absorption of additives, variable depletionof substances, and the like, along the length of intermediate coresection 40. Optionally, the material compositions of the segments 41 and42 may be different materials with inherently differing mechanicalproperties, with the segments bonded or otherwise joined at the segmentjunctions.

[0030] As the intermediate core section 40 is bent to conform to acurved vessel 44 (shown in phantom), the longitudinal axis 43 throughthe stiff segments 41 is bent little or negligibly, while thelongitudinal axis through the flexible core segments 42 is bent with agreater curvature. This causes the intermediate core section 40 to bendin a discontinuous or intermittent manner as described in the embodimentshown in FIG. 1.

[0031] While the above embodiments have been described in terms ofdimensional or compositional changes to affect the mechanical propertiesof the relatively stiff or the relative flexible intermediate coresegments, those skilled in the art will recognize that both dimensionaland compositional changes may be used to affect the desired variation inmechanical properties in the intermediate core section. Other methodsfor affecting a change in properties from core segment to core segmentwould include providing stiffening sheaths along the intermediate coresection. Other methods include having a braided core member with theangle and pattern of the braid being modified to impart the alternatingstiffness. Moreover, various modification and improvements may be madeto the invention without departing from the scope thereof. Terms such aselement, member, device, section, segment and words of similar importwhen used herein shall not be construed as invoking the provisions of 35U.S.C. §112(6) unless the following claims expressly use the term“means” or “step” followed by a particular function.

What is claimed is:
 1. A guide wire for intraluminal deployment of anelongated medical device within a patient, comprising: an elongate coremember having a proximal core section, a distal core section, and anintermediate core section disposed between the proximal and distal coresections which has a plurality of intermediate core segments whichalternate between relatively stiff and relatively flexible intermediatecore segments.
 2. The guide wire of claim 1 wherein the flexibleintermediate segments have smaller transverse cross-sectional areasrelative to the transverse cross sectional area of stiff segmentsproximally adjacent thereto.
 3. The guide wire of claim 2 wherein thestiff and flexible segments of the intermediate core section havecircular transverse cross-sectional shapes.
 4. The guide wire of claim 1wherein the stiff intermediate core segments have a length in the rangeof about 0.5 to about 10 cm.
 5. The guide wire of claim 1 wherein thestiff intermediate core segments have a length in the range of about 1cm to about 5 cm.
 6. The guide wire of claim 5 wherein the ratio of thediameter of flexible segments to the diameter of adjacent stiff segmentportions is from about 0.25:1 to about 0.75:1.
 7. The guide wire ofclaim 2 wherein the intermediate core section has an undulatinglongitudinal exterior contour.
 8. The guide wire of claim 2 wherein theintermediate core section is formed at least in part of stainless steel.9. The guide wire of claim 2 wherein the intermediate core section isformed at least in part of a superelastic alloy.
 10. The guide wire ofclaim 1 wherein the flexible intermediate core segment is formed of amaterial which is less rigid than the material of which the relativelystiff intermediate core segments are formed.
 11. The guide wire of claim10 wherein the ratio of the rigidity of the stiff core segments to thestiffness of an adjacent flexible core segment is from about 1.1:1 toabout 1.7:1.
 12. The guide wire of claim 10 wherein the ratio of therigidity of the stiff core segments to the stiffness of an adjacentflexible core segment is from about 1.3:1 to about 1.5:1. 13 A guidewirefor the intracorporeal delivery of elongated therapeutic or diagnosticdevices, comprising: a. an elongated core member having a proximal coresection, a distal core section more flexible than the proximal coresection, and an intermediate core section disposed between the proximaland distal core sections which has a plurality of intermediate coresegments at least one of which is relatively stiff and an adjacent onewhich is relatively flexible, and b. a flexible body disposed about andsecured to the distal core section. 14 A method of advancing a catheterwithin a patient's body lumen, comprising: a. advancing a guidewireaccording to claim 11 through a patient's body lumen until the distalend of the guidewire extends beyond the procedure site within the bodylumen; b. advancing a catheter having a proximal end and a distal endover the guidewire within the body lumen; and c. longitudinally movingthe catheter or the guidewire or both so as to dispose the distal end ofthe catheter alternately over the stiff and flexible intermediate coresegments to cause the distal end of the catheter to oscillate laterally.15. An elongated core member for an intraluminal guidewire having aproximal core section, a distal core section more flexible than theproximal core section and an intermediate core section disposed betweenthe proximal core section and the distal core section which has aplurality of intermediate core segments at least one of which isrelatively stiff and an adjacent one is relatively flexible.